Acrylic resin as well as preparation method and application thereof

Abstract

The invention relates to the field of thermoplastic resin, in particular to acrylic resin and a preparation method and application thereof.The acrylic resin is of a core-shell structure and comprises an inner core A, a middle layer B coating the surface of the inner core A and a shell layer C coating the surface of the middle layer B; an inner core A, a middle layer B and a shell layer C of the acrylic resin all comprise a structural unit derived from a hard monomer and a structural unit derived from a soft monomer; the existence of the inner core can provide better cohesion, and secondly, the acrylic resin with the three-layer core-shell structure has glass transition temperatures in three temperature ranges recorded in the specification, so that the impact strength of the PMMA resin is improved on the basis of maintaining high transparency.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of thermoplastic resin, in particular to an acrylic resin and a preparation method and application thereof. BACKGROUND

[0002] PMMA resin, the full name of which is polymethyl methacrylate in Chinese, is commonly known as organic glass or acrylic, which is a very important transparent polymer material in plastics at present. It has high transparency, high gloss and excellent weather resistance, and is widely used in the fields of building, electronics, automobiles and the like. However, the PMMA has obvious disadvantages, such as brittleness, notch sensitivity and low impact strength, which limit the application of the material itself. A common modification method is to add an impact-resistant modifier with a rubber phase. The addition of the modifier significantly improves the impact resistance, but has an adverse effect on the transparency of the PMMA resin. SUMMARY

[0003] The present application provides an acrylic resin and a preparation method and application thereof, so as to solve the problem that the existing modifier cannot improve the impact strength while maintaining the high transparency of the PMMA resin.

[0004] To this end, in a first aspect, the present application provides an acrylic resin, which is of a core-shell structure and comprises an inner core A, an intermediate layer B coated on the surface of the inner core A, and a shell layer C coated on the surface of the intermediate layer B; the inner core A, the intermediate layer B and the shell layer C of the acrylic resin each comprise a structural unit derived from a hard monomer and a structural unit derived from a soft monomer, and the acrylic resin has first, second and third glass transition temperatures at temperatures Tg1 of 20-40℃, Tg2 of -40- -20℃ and Tg3 of 80-100℃, respectively, which are determined by a differential scanning calorimeter at a temperature rising rate of 10℃ / min.

[0005] In some embodiments, the hard monomer used in the inner core A, the intermediate layer B and the shell layer C of the acrylic resin is independently selected from one or both of styrene and methyl methacrylate; In some embodiments, the soft monomer used in the inner core A, the intermediate layer B and the shell layer C of the acrylic resin is independently selected from one or more of isooctyl acrylate, butyl acrylate, ethyl acrylate or methyl acrylate.

[0006] In a second aspect, the present application provides an acrylic resin, which is of a core-shell structure and comprises an inner core A, an intermediate layer B coated on the surface of the inner core A, and a shell layer C coated on the surface of the intermediate layer B; The raw materials for preparing kernel A include a first hard monomer and a first soft monomer. Based on the total mass of the first hard monomer and the first soft monomer in the raw materials for preparing kernel A, the mass percentage of the first hard monomer is 60-75%; preferably 62-72%. The raw materials for preparing intermediate layer B include a second hard monomer and a second soft monomer. Based on the total mass of the second hard monomer and the second soft monomer in the raw materials for preparing intermediate layer B, the mass percentage of the second hard monomer is 15-25%; preferably 17-22%. The raw materials for preparing shell C include a third hard monomer and a third soft monomer. Based on the total mass of the third hard monomer and the third soft monomer in the raw materials for preparing shell C, the mass percentage of the third hard monomer is 85-100%; preferably 90-95%.

[0007] In some embodiments, the first hard monomer, the second hard monomer, and the third hard monomer are independently selected from one or both of styrene and methyl methacrylate.

[0008] In some embodiments, the first soft monomer, the second soft monomer, and the third soft monomer are independently selected from one or more of isooctyl acrylate, butyl acrylate, ethyl acrylate, or methyl acrylate.

[0009] In some embodiments, the raw materials for preparing core A also include a first functional monomer and / or a first emulsifier.

[0010] In some specific embodiments, the mass ratio of the first functional monomer to the first hard monomer is 0.5-3.5:100-300; preferably 1-3:120-280.

[0011] In some specific embodiments, the mass ratio of the first emulsifier to the first hard monomer is 0.5-3:100-300; preferably 1-2:120-280.

[0012] In some embodiments, the raw materials for preparing intermediate layer B also include a second functional monomer and / or a first hydroxyl monomer and / or a second emulsifier.

[0013] In some specific embodiments, the mass ratio of the second functional monomer to the second hard monomer is 5-15:120-260; preferably 6-13:130-210.

[0014] In some specific embodiments, the mass ratio of the first hydroxyl monomer to the second hard monomer is 5-13:120-260; preferably 6-12:130-210.

[0015] In some specific embodiments, the mass ratio of the second emulsifier to the second hard monomer is 2-8:120-260; preferably 3-8:130-210.

[0016] In some embodiments, the raw materials for preparing shell C also include a second hydroxyl monomer and / or a chain transfer agent and / or a third emulsifier.

[0017] In some specific embodiments, the mass ratio of the second hydroxyl monomer to the third hard monomer is 0.5-5:200-560; preferably 1-4:215-530.

[0018] In some specific embodiments, the mass ratio of the chain transfer agent to the third hard monomer is 0.5-3:200-560; preferably 0.8-2.5:215-530.

[0019] In some specific embodiments, the mass ratio of the third emulsifier to the third hard monomer is 0.5-4:200-560; preferably 0.5-3:215-530.

[0020] In some embodiments, the first functional monomer and the second functional monomer are independently selected from one or more of allyl methacrylate, ethylene glycol dimethacrylate, butanediol dimethacrylate, and divinylbenzene.

[0021] In some embodiments, the chain transfer agent is one or more of dodecyl mercaptan and n-octyl mercaptan.

[0022] In some embodiments, the first hydroxy monomer and the second hydroxy monomer are independently selected from one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl acrylate.

[0023] In some embodiments, the first emulsifier, the second emulsifier, and the third emulsifier are independently selected from one or more of disodium dodecyl diphenyl ether sulfonate, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfate.

[0024] In some embodiments, the amount of the second hydroxyl monomer used in the raw materials for preparing the acrylic resin is less than the amount of the first hydroxyl monomer.

[0025] In some embodiments, the ratio of the total mass of the first hard monomer and the first soft monomer, the total mass of the second hard monomer and the second soft monomer to the total mass of the third hard monomer and the third soft monomer is 10-25%:40-75%:10-40%; preferably 10-20%:50-65%:15-35%.

[0026] Thirdly, this application also provides a method for preparing any of the above-mentioned acrylic resins, comprising the following steps: Step S1: Mix the first hard monomer, the first soft monomer, the first functional monomer with the first emulsifier and water to prepare preemulsion I; mix the second soft monomer, the second functional monomer, the first hydroxyl monomer with the second emulsifier and water, and some or all of the second hard monomer to prepare preemulsion II; mix the third hard monomer, the third soft monomer, the chain transfer agent, the second hydroxyl monomer with the third emulsifier and water to prepare preemulsion III. Step S2: Preemulsion I undergoes a first-stage polymerization reaction in the presence of a first initiator to obtain core A; preemulsion II and core A undergo a second-stage polymerization reaction in the presence of a second initiator to obtain a block polymer containing core A and intermediate layer B; preemulsion III and the block polymer containing core A and intermediate layer B undergo a third-stage polymerization reaction in the presence of a third initiator to obtain acrylic resin.

[0027] Preferably, the mass ratio of the total mass of the first hard monomer and the first soft monomer to water in the preemulsion I is 140-400:40-100; more preferably, it is 160-320:50-90. Preferably, the mass ratio of the total mass of the first hard monomer and the first soft monomer to water in the preemulsion II is 650-1030:300-500; more preferably, it is 800-1000:350-450. Preferably, the mass ratio of the total mass of the first hard monomer and the first soft monomer to water in emulsion III is 240-560:100-300; more preferably, it is 260-550:120-280.

[0028] Preferably, when the preemulsion II contains a portion of the second hard monomer, the remaining portion of the second hard monomer is simultaneously incorporated into the reaction system by first mixing it into the preemulsion II and then into the reaction system during the second stage polymerization reaction.

[0029] In some embodiments, the first initiator, the second initiator, and the third initiator independently include thermal initiators and / or combination initiators of redox initiators and accelerators.

[0030] In some embodiments, the thermal initiator is selected from one or more of potassium persulfate and sodium persulfate.

[0031] In some embodiments, the redox initiator includes a first oxidant and a first reductant, wherein the first oxidant is selected from one or two of tert-butyl hydroperoxide and cumene hydroperoxide, and the first reductant is selected from one or two of sodium formaldehyde sulfoxylate, sodium metabisulfite, and sodium bisulfite.

[0032] In some embodiments, the accelerator comprises a combination of EDTA and ferrous sulfate.

[0033] This application does not limit the amount of the first initiator, the second initiator, the third initiator, and the accelerator. Conventional amounts in the art can be used. For example, the amount of initiator can be 0.1 to 0.5 wt% of the total mass of the soft monomer and the hard monomer, and the amount of accelerator can be 0.01 to 0.05 wt% of the total mass of the soft monomer and the hard monomer.

[0034] In some implementations, a post-processing step is included after the third-stage polymerization reaction.

[0035] In some embodiments, the post-processing includes mixing in a second oxidant and a second reducing agent to carry out an oxidation reaction.

[0036] In some embodiments, the post-processing includes the step of mixing in a neutralizing agent to carry out a neutralization reaction.

[0037] In some embodiments, the post-processing includes the step of incorporating a coagulant.

[0038] This application does not limit the types and amounts of the second oxidant, second reducing agent, neutralizing agent, and coagulant; conventional components and amounts in the art can be used. For example, the amount of neutralizing agent added is such that the pH of the neutralized emulsion is 7-9. The amounts of the second oxidant and second reducing agent can be 0.05-0.5 wt% of the total mass of the soft and hard monomers. The amount of coagulant can be 1-5 wt% of the total mass of the soft and hard monomers.

[0039] For example, the second oxidant can be selected from one or two of tert-butyl hydroperoxide and cumene hydroperoxide; the second reducing agent can be selected from one or two of sodium formaldehyde sulfoxylate, sodium metabisulfite, and sodium bisulfite; the neutralizing agent can be potassium hydroxide and / or sodium hydroxide; and the coagulant can be one or two of calcium chloride, magnesium sulfate, and calcium acetate. The amount of neutralizing agent added is such that the pH of the neutralized emulsion is 7-9.

[0040] In some specific embodiments, the preparation method of the acrylic resin includes the following steps: Step S1: Mix the first hard monomer, the first soft monomer, the first functional monomer, the first emulsifier, and water to obtain preemulsion I; mix the second soft monomer, the second functional monomer, the first hydroxyl monomer, the second emulsifier, water, and part or all of the second hard monomer to obtain preemulsion II; mix the third hard monomer, the third soft monomer, the chain transfer agent, the second hydroxyl monomer, and the third emulsifier to obtain emulsion III; Step S2: Add a portion of the first initiator solution to water and mix to form a base solution. Add the remaining portion of the first initiator solution and preemulsion I dropwise to carry out the first stage polymerization reaction, obtaining a reaction solution containing core A. Add the second initiator solution and preemulsion II dropwise to the reaction solution containing core A to carry out the second stage polymerization reaction, obtaining a reaction solution containing block polymer A and intermediate layer B. Add an accelerator solution to the reaction solution containing block polymer A and intermediate layer B, and then add the third initiator solution and preemulsion III dropwise to carry out the third stage polymerization reaction, obtaining a reaction solution containing acrylic resin. Step S3: The reaction solution containing acrylic resin is mixed with the second oxidant solution and the second reducing agent solution for reaction. Then, a neutralizing agent solution and a coagulant solution are mixed in. After solid-liquid separation, the mixture is dried to obtain acrylic resin.

[0041] In some preferred embodiments, when the preemulsion II contains a portion of the second hard monomer, in step S2, after adding 50-70% of the preemulsion II to the reaction solution containing the core A, the remaining portion of the second hard monomer is added to the preemulsion II while simultaneously adding the preemulsion II to the reaction solution containing the core A; more preferably, the mass of the second hard monomer added to the preemulsion II accounts for 25%-65% of the total mass of hard monomers in the raw materials for preparing the intermediate layer B.

[0042] Fourthly, this application provides the application of any of the above-described acrylic resins or acrylic resins prepared by any of the above-described preparation methods in improving the optical and / or mechanical properties of thermoplastic resins; optionally, the thermoplastic resin includes polymethyl methacrylate.

[0043] Fifthly, this application provides a modified PMMA resin, comprising any of the acrylic resins described above or the acrylic resins prepared by any of the preparation methods described above, as well as polymethyl methacrylate.

[0044] In some specific embodiments, the acrylic resin and the polymethyl methacrylate are in a ratio of 0.5~2:1~5.

[0045] In this application, "simultaneous addition" or "simultaneous dripping" refers to the simultaneous but independent addition of two different liquid materials to a reaction vessel at a controlled rate in a reaction system. The start and end times of the addition of the two different liquid materials are the same, and the dripping rates may be the same or different.

[0046] The technical solution of this invention has the following advantages: 1. The acrylic resin provided by the present invention has a core-shell structure, comprising a core A, an intermediate layer B covering the surface of the core, and a shell layer C covering the surface of the intermediate layer B; the core A, intermediate layer B, and shell layer C of the acrylic resin each contain structural units derived from hard monomers and structural units derived from soft monomers; the acrylic resin has a first, a second, and a third glass transition temperature at a temperature Tg1 of 20℃~40℃, a temperature Tg2 of -40℃~-20℃, and a temperature Tg3 of 80℃~100℃, respectively; the glass transition temperature is determined by differential scanning calorimetry at a heating rate of 10℃ / min.

[0047] First, the acrylic resin employing a three-layer core-shell structure provides superior cohesive strength due to the presence of the core. Second, the three-layer core-shell structure allows the acrylic resin to undergo glass transitions within the three temperature ranges mentioned above, resulting in three glass transition temperatures that enhance impact resistance while maintaining high transparency. When Tg1 is below 20°C, the inner layer becomes too soft and cannot provide sufficient cohesive strength, leading to a decrease in impact strength. When Tg1 is above 40°C, the inner layer becomes too hard, also reducing impact strength. When Tg2 is below -40°C, optical properties deteriorate. When Tg2 is above -20°C, the rubber becomes too hard, further reducing impact strength. When Tg3 is below 80°C, the compatibility between the resin and the PMMA substrate decreases significantly, causing processing problems.

[0048] 2. The acrylic resin provided by the present invention has a core-shell structure, comprising a core A, an intermediate layer B covering the surface of the core, and a shell layer C covering the surface of the intermediate layer B; The raw materials for preparing core A include a first hard monomer and a first soft monomer. Based on the total mass of the first hard monomer and the first soft monomer in the raw materials for preparing core A, the mass percentage of the first hard monomer is 60-75%; preferably 62-72%. The raw materials for preparing intermediate layer B include a second hard monomer and a second soft monomer. Based on the total mass of the second hard monomer and the second soft monomer in the raw materials for preparing intermediate layer B, the mass percentage of the second hard monomer is 15-25%; preferably 17-22%. The raw materials for preparing shell layer C include a third hard monomer and a third soft monomer. Based on the total mass of the third hard monomer and the third soft monomer in the raw materials for preparing shell layer C, the mass percentage of the third hard monomer is 85-100%; preferably 90-95%. By using a three-layer core-shell structure acrylic resin and by controlling the mass percentage of hard and soft monomers in the raw materials for preparing the three layers within the above ranges, the glass transition temperatures of the three layers are sequentially controlled at Tg1, Tg2, and Tg3, thereby improving the impact resistance of the PMMA resin while maintaining high transparency.

[0049] 3. The acrylic resin provided by the present invention further includes functional monomers (specifically, a first functional monomer and a second functional monomer) in the raw materials of the core A and / or intermediate layer B. The use of functional monomers can enhance the degree of crosslinking of chain segments, thereby providing sufficient cohesive force.

[0050] 4. The acrylic resin provided by the present invention further includes hydroxyl monomers (specifically, a first hydroxyl monomer and a second hydroxyl monomer) in the raw materials of the shell layer C and / or the intermediate layer B. The use of hydroxyl monomers can increase the interaction force between the core and shell structures, thereby further improving the resistance to yellowing and optical properties while ensuring impact strength.

[0051] In particular, by limiting the amount of the second hydroxyl monomer to be less than that of the first hydroxyl monomer, the interaction between the second and third layers can be significantly enhanced, while ensuring that the interaction between the shell layer and the matrix resin is not too strong, which could lead to processing problems and particle aggregation.

[0052] 5. The acrylic resin provided by the present invention, in step S2, after adding 50-70% of pre-emulsion II to the reaction solution containing core A, simultaneously adding the remaining portion of the second hard monomer to the pre-emulsion II; particularly, controlling the mass of the second hard monomer added to the pre-emulsion II to account for 25%-65% of the total mass of hard monomers in the pre-emulsion II can adjust the monomer polymerization uniformity of the intermediate layer, thereby providing superior impact strength while ensuring good optical properties. Attached Figure Description

[0053] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0054] Figure 1 This is a DSC diagram of the acrylic resin prepared in Example 1 of this application. Detailed Implementation The following embodiments are provided to better understand the present invention, but the following embodiments do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the scope of protection of the present invention.

[0055] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0056] Test method for glass transition temperature (Tg): Take 3 grams of the acrylate resin, spread it evenly on 5cm*5cm centrifugal paper, dry it in an oven at 50℃ for 24 hours, and take the dried acrylate polymer to determine it by differential scanning calorimetry (DSC) at a heating rate of 10℃ / min.

[0057] Example 1 This embodiment provides an acrylic resin and its preparation method. The acrylic resin has a core-shell structure, comprising a core A, an intermediate layer B covering the surface of the core A, and a shell layer C covering the surface of the intermediate layer B. The core A, intermediate layer B, and shell layer C of the acrylic resin all contain structural units derived from hard monomers and structural units derived from soft monomers. (See...) Figure 1 As shown, the acrylic resin in this embodiment has three glass transition temperatures, namely 33.09°C, -34.09°C, and 98.82°C.

[0058] Its preparation method includes the following steps: 1. Preparation steps of raw material liquid (1) The composition of preemulsion I is as follows: 90g deionized water, 1g sodium dodecylbenzenesulfonate, 100g methyl methacrylate, 50g styrene, 70g butyl acrylate and 1g ethylene glycol dimethacrylate.

[0059] Preparation method: Add the above substances to an emulsification vessel equipped with a stirring device and stir thoroughly to obtain pre-emulsion I.

[0060] (2) The composition of preemulsion II is as follows: 400g deionized water, 3g sodium dodecylbenzenesulfonate, 80g styrene, 800g butyl acrylate, 6g hydroxyethyl acrylate, 2g ethylene glycol dimethacrylate and 4g allyl methacrylate.

[0061] Preparation method: Add the above substances to an emulsification vessel equipped with a stirring device and stir thoroughly to obtain pre-emulsion II.

[0062] (3) The composition of emulsion III is as follows: 100g deionized water, 3g sodium dodecylbenzenesulfonate, 380g methyl methacrylate, 20g ethyl acrylate, 2g hydroxyethyl methacrylate and 1g n-dodecyl mercaptan.

[0063] Preparation method: Add the above substances to an emulsification vessel equipped with a stirring device and stir thoroughly to obtain emulsion III.

[0064] (4) Preparation of other functional solutions: Weigh 0.5g of sodium persulfate and dissolve it in 80g of deionized water to prepare the first initiator solution. Weigh 2.5g of sodium persulfate and dissolve it in 150g of deionized water to prepare the second initiator solution. Weigh 2g of tert-butyl hydroperoxide and dissolve it in 100g of deionized water to prepare the first oxidant solution. Weigh 2g of sodium metabisulfite and dissolve it in 100g of deionized water to prepare the second reducing agent solution. Dissolve 0.06g of EDTA and 0.02g of ferrous sulfate in 2g of water to prepare the accelerator solution. Dissolve 8g of TBHP (tert-butyl hydroperoxide) in 20g of water to prepare the second oxidant solution. Dissolve 6g of sodium formaldehyde sulfoxylate in 20g of water to prepare the second reducing agent solution. Weigh 60g of calcium chloride and dissolve it in 6kg of deionized water to prepare a calcium chloride solution.

[0065] 2. Polymerization reaction (1) Add 800g of deionized water to the reactor and heat it to 80℃. Add 20g of the prepared first initiator solution to the reactor first, disperse for 3min, and then add the preemulsion I and the remaining first initiator solution dropwise simultaneously. Control the reaction temperature at 83-85℃ and add dropwise for 1h until all the preemulsion I and the first initiator solution are added to the reactor to obtain the reaction solution containing core A.

[0066] (2) Pre-emulsion II and the second initiator solution are added dropwise to the reactor simultaneously, and the reaction temperature is controlled at 80-83℃. After 50% of the emulsion II has been added, 100g of styrene (the second hard monomer added) is added to the pre-emulsion II at the same time and stirred evenly. The addition is continued for 1.5h until all the pre-emulsion II and the second initiator solution are added to the reactor (the second hard monomer added is added to the reactor along with the pre-emulsion II), and a reaction solution of polymer containing core A and intermediate layer B is obtained.

[0067] (3) Add the accelerator solution to the reactor all at once, and maintain stirring for 3 minutes after addition. Simultaneously add emulsion III, the first oxidant solution, and the first reducing agent solution to the reactor, controlling the reaction temperature at 70-75℃, and add for 3 hours until all the above solutions are added to the reactor. After the addition is completed, keep the temperature for 30 minutes, and then simultaneously add the second oxidant solution and the second reducing agent solution to the reactor. Cool down to 45℃, add 1g of sodium hydroxide to adjust the pH of the emulsion to 7-8. Add calcium chloride solution to the reactor, wash with water, centrifuge, and dry to obtain the acrylic resin copolymer.

[0068] Example 2 This embodiment provides an acrylic resin and its preparation method. The acrylic resin has a core-shell structure, comprising a core A, an intermediate layer B covering the surface of the core A, and a shell layer C covering the surface of the intermediate layer B. The core A, intermediate layer B, and shell layer C of the acrylic resin all contain structural units derived from hard monomers and structural units derived from soft monomers. The acrylic resin has three glass transition temperatures, as shown in Table 1. The preparation method of the acrylic resin includes the following steps: 1. Preparation steps of raw material liquid (1) The composition of preemulsion I is as follows: 50g deionized water, 2g sodium dodecyl sulfate, 120g methyl methacrylate, 70g methyl acrylate and 3g allyl methacrylate.

[0069] Preparation method: Add the above substances to an emulsification vessel equipped with a stirring device and stir thoroughly to obtain pre-emulsion I.

[0070] (2) The composition of preemulsion II is as follows: 500g deionized water, 5g sodium dodecyl sulfate, 60g styrene, 650g isooctyl acrylate, 8g hydroxyethyl methacrylate, 3g allyl methacrylate, and 2g ethylene glycol dimethacrylate.

[0071] Preparation method: Add the above substances to an emulsification vessel equipped with a stirring device and stir thoroughly to obtain pre-emulsion II.

[0072] (3) The composition of emulsion III is as follows: 200g deionized water, 2g sodium dodecyl sulfate, 390g methyl methacrylate, 30g methyl acrylate, 1g hydroxyethyl acrylate and 0.8g n-octyl mercaptan.

[0073] Preparation method: Add the above substances to an emulsification vessel equipped with a stirring device and stir thoroughly to obtain emulsion III.

[0074] (4) Preparation of other functional solutions: Weigh 0.5g of potassium persulfate and dissolve it in 80g of deionized water to prepare the first initiator solution. Weigh 2.5g of potassium persulfate and dissolve it in 150g of deionized water to prepare the second initiator solution. Weigh 2g of cumene hydrogen peroxide and dissolve it in 100g of deionized water to prepare the first oxidant solution. Weigh 2g of sodium bisulfite and dissolve it in 100g of deionized water to prepare the second reducing agent solution. Dissolve 0.06g of EDTA and 0.02g of ferrous sulfate in 2g of water to prepare the accelerator solution. Dissolve 8g of TBHP in 20g of water to prepare the second oxidant solution. Dissolve 6g of sodium formaldehyde sulfoxylate in 20g of water to prepare the second reducing agent solution. Weigh 60g of calcium chloride and dissolve it in 6kg of deionized water to prepare a calcium chloride solution.

[0075] 2. Polymerization reaction (1) Add 800g of deionized water to the reactor and heat it to 80℃. Add 20g of the prepared first initiator solution to the reactor first, disperse for 3min, and then add the pre-emulsion I and the remaining first initiator solution dropwise simultaneously. Control the reaction temperature at 83-85℃ and add dropwise for 1h until all the pre-emulsion I and the first initiator solution are added to the reactor.

[0076] (2) Simultaneously add preemulsion II and the second initiator solution to the reactor, and control the reaction temperature at 80-83℃. After 50% of the emulsion II has been added, while continuing to add preemulsion II to the reactor, add 90g of styrene (the second hard monomer) to the preemulsion II at one time and stir evenly. Continue to add for 1.5h until all the preemulsion II and the second initiator solution have been added to the reactor.

[0077] (3) Add the accelerator solution to the reactor all at once, and maintain stirring for 3 minutes after addition. Simultaneously add emulsion III, the first oxidant solution, and the first reducing agent solution to the reactor, controlling the reaction temperature at 70-75℃, and add for 3 hours until all the above solutions are added to the reactor. After the addition is completed, keep the temperature for 30 minutes, and then simultaneously add the second oxidant solution and the second reducing agent solution to the reactor. Cool down to 45℃, add 1g of sodium hydroxide to adjust the pH of the emulsion to 7-8. Add 60g of calcium chloride solution to the reactor, wash with water, centrifuge, and dry to obtain the acrylic resin copolymer.

[0078] Example 3 This embodiment provides an acrylic resin and its preparation method. The acrylic resin has a core-shell structure, comprising a core A, an intermediate layer B covering the surface of the core A, and a shell layer C covering the surface of the intermediate layer B. The core A, intermediate layer B, and shell layer C of the acrylic resin all contain structural units derived from hard monomers and structural units derived from soft monomers. The acrylic resin has three glass transition temperatures, as shown in Table 1. The preparation of the acrylic resin includes the following steps: 1. Preparation steps of raw material liquid (1) The composition of preemulsion I is as follows: 60g deionized water, 1.5g sodium dodecylbenzenesulfonate, 170g methyl methacrylate, 50g styrene, 90g butyl acrylate and 1.5g ethylene glycol dimethacrylate.

[0079] Preparation method: Add the above substances to an emulsification vessel equipped with a stirring device and stir thoroughly to obtain pre-emulsion I.

[0080] (2) The composition of preemulsion II is as follows: 300g deionized water, 8g sodium dodecylbenzenesulfonate, 90g styrene, 800g butyl acrylate, 12g hydroxyethyl acrylate, 9g ethylene glycol dimethacrylate and 3g allyl methacrylate.

[0081] Preparation method: Add the above substances to an emulsification vessel equipped with a stirring device and stir thoroughly to obtain pre-emulsion II.

[0082] (3) The composition of emulsion III is as follows: 280g deionized water, 0.5g sodium dodecylbenzenesulfonate, 500g methyl methacrylate, 30g ethyl acrylate, 4g hydroxyethyl methacrylate and 2.5g n-dodecyl mercaptan.

[0083] Preparation method: Add the above substances to an emulsification vessel equipped with a stirring device and stir thoroughly to obtain emulsion III.

[0084] (4) Preparation of other functional solutions: Weigh 0.5g of sodium persulfate and dissolve it in 80g of deionized water to prepare the first initiator solution. Weigh 2.5g of sodium persulfate and dissolve it in 150g of deionized water to prepare the second initiator solution. Weigh 2g of tert-butyl hydroperoxide and dissolve it in 100g of deionized water to prepare the first oxidant solution. Weigh 2g of sodium metabisulfite and dissolve it in 100g of deionized water to prepare the second reducing agent solution. Dissolve 0.06g of EDTA and 0.02g of ferrous sulfate in 2g of water to prepare the accelerator solution. Dissolve 8g of TBHP in 20g of water to prepare the second oxidant solution. Dissolve 6g of sodium formaldehyde sulfoxylate in 20g of water to prepare the second reducing agent solution. Weigh 60g of calcium chloride and dissolve it in 6kg of deionized water to prepare a calcium chloride solution.

[0085] 2. Polymerization reaction (1) Add 800g of deionized water to the reactor and heat it to 80℃. Add 20g of the prepared first initiator solution to the reactor first, disperse for 3min, and then add the pre-emulsion I and the remaining first initiator solution dropwise simultaneously. Control the reaction temperature at 83-85℃ and add dropwise for 1h until all the pre-emulsion I and the first initiator solution are added to the reactor.

[0086] (2) Simultaneously add pre-emulsion II and the second initiator solution to the reactor, and control the reaction temperature at 80-83℃. After 50% of the emulsion II has been added, while continuing to add pre-emulsion II to the reactor, add 80g of styrene (the second hard monomer) to the pre-emulsion II at one time and stir evenly. Continue to add for 1.5h until all the pre-emulsion II and the second initiator solution have been added to the reactor.

[0087] (3) Add the accelerator solution to the reactor all at once, and maintain stirring for 3 minutes after addition. Simultaneously add emulsion III, the first oxidant solution, and the first reducing agent solution to the reactor, controlling the reaction temperature at 70-75℃, and add for 3 hours until all the above solutions are added to the reactor. After the addition is completed, keep the temperature for 30 minutes, and then simultaneously add the second oxidant solution and the second reducing agent solution to the reactor. Cool down to 45℃, add 1g of sodium hydroxide to adjust the pH of the emulsion to 7-8. Add 60g of calcium chloride solution to the reactor, wash with water, centrifuge, and dry to obtain the acrylic resin copolymer.

[0088] Example 4 The only difference from Example 1 is that the amount of methyl methacrylate and butyl acrylate in the composition of preemulsion I is adjusted to 85g.

[0089] Example 5 The only difference from Example 1 is that the amount of methyl methacrylate in the composition of preemulsion I is adjusted to 158g and the amount of butyl acrylate is adjusted to 80g.

[0090] Example 6 The only difference from Example 1 is that the amount of styrene in the composition of preemulsion II is adjusted to 100g and the amount of butyl acrylate is adjusted to 600g.

[0091] Example 7 The only difference from Example 1 is that the amount of styrene in the composition of preemulsion II is adjusted to 50g and the amount of butyl acrylate is adjusted to 860g.

[0092] Example 8 The only difference from Example 1 is that in the composition of preemulsion III, the amount of methyl methacrylate is adjusted to 380g and the amount of ethyl acrylate is adjusted to 50g.

[0093] Example 9 The only difference from Example 1 is that in the composition of preemulsion III, the amount of methyl methacrylate is adjusted to 550g and the amount of ethyl acrylate is adjusted to 20g.

[0094] Example 10 The only difference from Example 1 is that the amount of styrene in the composition of preemulsion II is adjusted to 180g, and no styrene is added to preemulsion II during the entire process of adding preemulsion II to the reactor in step (2) of the polymerization reaction.

[0095] Example 11 The only difference from Example 1 is that the addition of hydroxyethyl acrylate and hydroxyethyl methacrylate was omitted in the preparation of preemulsion II and preemulsion III, respectively.

[0096] Example 12 The only difference from Example 1 is that the amounts of hydroxyethyl acrylate and hydroxyethyl methacrylate in preemulsion II and preemulsion III are adjusted to 3g and 5g, respectively, so that the amount of the second hydroxy monomer added is greater than the amount of the first hydroxy monomer added.

[0097] Example 13 The only difference from Example 1 is that the amount of hydroxyethyl acrylate and hydroxyethyl methacrylate in preemulsion II and preemulsion III is adjusted to 4g, so that the amount of the second hydroxy monomer added is equal to the amount of the first hydroxy monomer added.

[0098] Comparative Example 1 The only difference from Example 1 is that the preparation of preemulsion I and the first initiator solution is omitted, and the polymerization reaction is carried out using the following method: (1) Add 800g of deionized water to the reactor and heat it to 80℃. First, add 20g of the prepared second initiator solution to the reactor. Simultaneously add preemulsion II and the second initiator solution to the reactor. Control the reaction temperature at 80-83℃. After adding 50% of emulsion II, add 100g of styrene (the second hard monomer added) to the preemulsion II at the same time as adding preemulsion II to the reactor. Continue adding for 1.5h until all the preemulsion II and the second initiator solution are added to the reactor (the second hard monomer added is added to the reactor along with the preemulsion II).

[0099] (2) Add the accelerator solution to the reactor all at once, and maintain stirring for 3 minutes after addition. Simultaneously add emulsion III, the first oxidant solution, and the first reducing agent solution to the reactor, controlling the reaction temperature at 70-75℃, and add for 3 hours until all the above solutions are added to the reactor. After the addition is completed, keep the temperature for 30 minutes, and then simultaneously add the second oxidant solution and the second reducing agent solution to the reactor. Cool down to 45℃ and add 1g of sodium hydroxide. Add 60g of calcium chloride solution to the reactor, wash with water, centrifuge, and dry to obtain the acrylic resin copolymer.

[0100] Comparative Example 2 The only difference from Example 1 is that the preparation of preemulsion II and the second initiator solution is omitted, and the polymerization reaction is carried out using the following method: (1) Add 800g of deionized water to the reactor and heat it to 80℃. Add 20g of the prepared first initiator solution to the reactor first, disperse for 3min, and then add the pre-emulsion I and the remaining first initiator solution dropwise simultaneously. Control the reaction temperature at 83-85℃ and add dropwise for 1h until all the pre-emulsion I and the first initiator solution are added to the reactor.

[0101] (2) Add the accelerator solution to the reactor all at once, and maintain stirring for 3 minutes after addition. Simultaneously add emulsion III, the first oxidant solution, and the first reducing agent solution to the reactor, controlling the reaction temperature at 70-75℃, and add for 3 hours until all the above solutions are added to the reactor. After the addition is completed, keep the temperature for 30 minutes, and then simultaneously add the second oxidant solution and the second reducing agent solution to the reactor. Cool down to 45℃ and add 1g of sodium hydroxide. Add 60g of calcium chloride solution to the reactor, wash with water, centrifuge, and dry to obtain the acrylic resin copolymer.

[0102] Comparative Example 3 The only difference from Example 1 is that the preparation of pre-emulsion III, accelerator solution, first oxidant solution, and first reducing agent solution is omitted, and the polymerization reaction is carried out using the following method: (1) Add 800g of deionized water to the reactor and heat it to 80℃. Add 20g of the prepared first initiator solution to the reactor first, disperse for 3min, and then add the pre-emulsion I and the remaining first initiator solution dropwise simultaneously. Control the reaction temperature at 83-85℃ and add dropwise for 1h until all the pre-emulsion I and the first initiator solution are added to the reactor.

[0103] (2) Pre-emulsion II and the second initiator solution were simultaneously added dropwise to the reactor, and the reaction temperature was controlled at 80-83℃. After 50% of emulsion II was added, 100g of styrene (the supplementary second hard monomer) was added to the pre-emulsion II at the same time as it was added dropwise to the reactor. The addition was continued for 1.5h until all of the pre-emulsion II and the second initiator solution were added to the reactor (the supplementary second hard monomer was added to the reactor along with the pre-emulsion II). After the addition was completed, the temperature was maintained for 30min, and then the second oxidant solution and the second reducing agent solution were simultaneously added dropwise to the reactor. The temperature was lowered to 45℃, and 1g of sodium hydroxide was added. 60g of calcium chloride solution was added to the reactor, and after washing with water, centrifugation, and drying, the acrylic resin copolymer was obtained.

[0104] Comparative Example 4 The only difference from Example 1 is that in the composition of preemulsion I, the amount of methyl methacrylate is adjusted to 90g, the amount of styrene is adjusted to 10g, and the amount of butyl acrylate is adjusted to 120g, so that the Tg1 of the final acrylic resin is different, as shown in Table 1.

[0105] Comparative Example 5 The only difference from Example 1 is that in the composition of preemulsion I, the amount of methyl methacrylate is adjusted to 160g, the amount of styrene is adjusted to 10g, and the amount of butyl acrylate is adjusted to 50g, so that the Tg1 of the final acrylic resin is different, as shown in Table 1.

[0106] Comparative Example 6 The only difference in Example 1 is that the amount of styrene in the composition of preemulsion II is adjusted to 44g, 900g of isooctyl acrylate is used instead of 800g of butyl acrylate, and the amount of the added second hard monomer is adjusted to 66g, resulting in a different Tg2 of the final acrylic resin, as shown in Table 1.

[0107] Comparative Example 7 The only difference in Example 1 is that the amount of styrene in the composition of preemulsion II is adjusted to 120g and the amount of butyl acrylate is adjusted to 760g, resulting in a different Tg2 of the final acrylic resin, as shown in Table 1.

[0108] Comparative Example 8 The only difference in Example 1 is that the amount of methyl methacrylate in the composition of preemulsion III is adjusted to 350g and the amount of ethyl acrylate is adjusted to 50g, resulting in a different Tg3 of the final acrylic resin, as shown in Table 1.

[0109] Table 1 Glass transition temperatures of acrylic resins

[0110] Application examples The acrylic resins prepared in each example and comparative example were compounded with PMMA resin (purchased from Wanhua, model: HD01) at a mass ratio of 1:3. The mixture was then compounded and granulated using a Thermo-Jakke twin-roll mill from Germany at a processing temperature of 220°C and a compounding time of 5 minutes to obtain the modified PMMA resin.

[0111] Performance tests were conducted on each group of modified PMMA resins.

[0112] (1) Optical properties: The modified PMMA resin was pressed into 2mm tablets on a tablet press and the transparency and haze were tested on a photometric haze meter according to the ASTM D-1003 test method. The modified PMMA resin was pressed into 3mm tablets on a tablet press and the yellowness value and b value were tested on a yellowness meter according to the GB / T 39822 test method.

[0113] (2) Mechanical properties: The modified PMMA resin was made into standard impact specimens with a thickness of 4 mm according to ASTM D256. The notched impact strength of the cantilever beam was measured after V-shaped notches were cut on the specimens using a notching machine.

[0114] The test results are shown in Table 2.

[0115] Table 2 Test Results

[0116] As can be seen from the above results, compared with the comparative examples, the PMMA resin provided in each embodiment of this application can achieve both good optical properties and strong impact resistance.

[0117] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An acrylic resin, characterized in that, The acrylic resin has a core-shell structure, comprising a core A, an intermediate layer B covering the surface of the core A, and a shell layer C covering the surface of the intermediate layer B. The core A, intermediate layer B, and shell layer C of the acrylic resin each contain structural units derived from hard monomers and structural units derived from soft monomers. The acrylic resin has a first glass transition temperature (Tg1) at 20℃~40℃, a second glass transition temperature (Tg2) at -40℃~-20℃, and a third glass transition temperature (Tg3) at 80℃~100℃. The first glass transition temperature, the second glass transition temperature, and the third glass transition temperature are measured by differential scanning calorimetry at a heating rate of 10℃ / min.

2. An acrylic resin, characterized in that, The acrylic resin has a core-shell structure, comprising a core A, an intermediate layer B covering the surface of the core A, and a shell layer C covering the surface of the intermediate layer B. The raw materials for preparing kernel A include a first hard monomer and a first soft monomer. Based on the total mass of the first hard monomer and the first soft monomer in the raw materials for preparing kernel A, the mass percentage of the first hard monomer is 60-75%; preferably 62-72%. The raw materials for preparing intermediate layer B include a second hard monomer and a second soft monomer. Based on the total mass of the second hard monomer and the second soft monomer in the raw materials for preparing intermediate layer B, the mass percentage of the second hard monomer is 15-25%; preferably 17-22%. The raw materials for preparing shell C include a third hard monomer and a third soft monomer. Based on the total mass of the third hard monomer and the third soft monomer in the raw materials for preparing shell C, the mass percentage of the third hard monomer is 85-100%; preferably 90-95%. Optionally, the first hard monomer, the second hard monomer, and the third hard monomer are independently selected from one or two of styrene and methyl methacrylate; Optionally, the first soft monomer, the second soft monomer, and the third soft monomer are independently selected from one or more of isooctyl acrylate, butyl acrylate, ethyl acrylate, or methyl acrylate.

3. The acrylic resin according to claim 2, characterized in that, At least one of the following must be met: A. The raw materials for preparing core A also include a first functional monomer and / or a first emulsifier; Optionally, the mass ratio of the first functional monomer to the first hard monomer is 0.5-3.5:100-300; preferably 1-3:120-280. Optionally, the mass ratio of the first emulsifier to the first hard monomer is 0.5-3:100-300; preferably 1-2:120-280. B. The raw materials for preparing intermediate layer B also include a second functional monomer and / or a first hydroxyl monomer and / or a second emulsifier; Optionally, the mass ratio of the second functional monomer to the second hard monomer is 5-15:120-260; preferably 6-13:130-210. Optionally, the mass ratio of the first hydroxyl monomer to the second hard monomer is 5-13:120-260; preferably 6-12:130-210. Optionally, the mass ratio of the second emulsifier to the second hard monomer is 2-8:120-260; preferably 3-8:130-210. C. The raw materials for preparing shell C also include a second hydroxyl monomer and / or a chain transfer agent and / or a third emulsifier; Optionally, the mass ratio of the second hydroxyl monomer to the third hard monomer is 0.5-5:200-560; preferably 1-4:215-530. Optionally, the mass ratio of the chain transfer agent to the third hard monomer is 0.5-3:200-560; preferably 0.8-2.5:215-530. Optionally, the mass ratio of the third emulsifier to the third hard monomer is 0.5-4:200-560; preferably 0.5-3:215-530. D. The ratio of the total mass of the first hard monomer and the first soft monomer, the total mass of the second hard monomer and the second soft monomer to the total mass of the third hard monomer and the third soft monomer is 10-25%:40-75%:10-40%; preferably 10-20%:50-65%:15-35%.

4. The acrylic resin according to claim 3, characterized in that, The first functional monomer and the second functional monomer are independently selected from one or more of allyl methacrylate, ethylene glycol dimethacrylate, butanediol dimethacrylate, and divinylbenzene; And / or, the chain transfer agent is one or more of dodecyl mercaptan and n-octyl mercaptan; And / or, the first hydroxy monomer and the second hydroxy monomer are independently selected from one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl acrylate; And / or, the first emulsifier, the second emulsifier, and the third emulsifier are independently selected from one or more of disodium dodecyl diphenyl ether sulfonate, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfate; And / or, in the raw materials for preparing the acrylic resin, the amount of the second hydroxyl monomer is less than the amount of the first hydroxyl monomer.

5. A method for preparing the acrylic resin according to any one of claims 1-4, characterized in that, Includes the following steps: Step S1: Mix the first hard monomer, the first soft monomer, the first functional monomer with the first emulsifier and water to prepare preemulsion I; mix the second soft monomer, the second functional monomer, the first hydroxyl monomer with the second emulsifier and water, and some or all of the second hard monomer to prepare preemulsion II; mix the third hard monomer, the third soft monomer, the chain transfer agent, the second hydroxyl monomer with the third emulsifier and water to prepare preemulsion III. Step S2: Preemulsion I undergoes a first-stage polymerization reaction in the presence of a first initiator to obtain core A; preemulsion II and core A undergo a second-stage polymerization reaction in the presence of a second initiator to obtain a block polymer containing core A and intermediate layer B; preemulsion III and the block polymer containing core A and intermediate layer B undergo a third-stage polymerization reaction in the presence of a third initiator to obtain acrylic resin. Preferably, the mass ratio of the total mass of the first hard monomer and the first soft monomer to water in the preemulsion I is 140-400:40-100; more preferably, it is 160-320:50-90. Preferably, the mass ratio of the total mass of the first hard monomer and the first soft monomer to water in the preemulsion II is 650-1030:300-500; more preferably, it is 800-1000:350-450. Preferably, the mass ratio of the total mass of the first hard monomer and the first soft monomer to water in emulsion III is 240-560:100-300; more preferably, it is 260-550:120-280. Preferably, when the preemulsion II contains a portion of the second hard monomer, the remaining portion of the second hard monomer is simultaneously incorporated into the reaction system by first mixing it into the preemulsion II and then into the reaction system during the second stage polymerization reaction.

6. The method for preparing acrylic resin according to claim 5, characterized in that, The first initiator, the second initiator, and the third initiator independently include thermal initiators and / or combination initiators of redox initiators and accelerators; Optionally, the thermal initiator is selected from one or more of potassium persulfate and sodium persulfate; Optionally, the redox initiator includes a first oxidant and a first reductant, wherein the first oxidant is selected from one or two of tert-butyl hydroperoxide and cumene hydroperoxide, and the first reductant is selected from one or two of sodium formaldehyde sulfoxylate, sodium metabisulfite, and sodium bisulfite. Optionally, the accelerator comprises a combination of EDTA and ferrous sulfate.

7. The method for preparing acrylic resin according to claim 5 or 6, characterized in that, Following the third-stage polymerization reaction, post-processing steps are also included; Optionally, the post-processing includes mixing in a second oxidant and a second reducing agent for reaction; Optionally, the post-processing includes the step of mixing in a neutralizing agent to carry out a neutralization reaction; Optionally, the post-processing includes the step of incorporating a coagulant.

8. The method for preparing acrylic resin according to claim 7, characterized in that, The preparation method of the acrylic resin includes the following steps: Step S1: Mix the first hard monomer, the first soft monomer, the first functional monomer, the first emulsifier, and water to obtain preemulsion I; mix the second soft monomer, the second functional monomer, the first hydroxyl monomer, the second emulsifier, water, and part or all of the second hard monomer to obtain preemulsion II; mix the third hard monomer, the third soft monomer, the chain transfer agent, the second hydroxyl monomer, and the third emulsifier to obtain emulsion III; Step S2: Add a portion of the first initiator solution to water and mix to form a base solution. Add the remaining portion of the first initiator solution and preemulsion I dropwise to carry out the first stage polymerization reaction, obtaining a reaction solution containing core A. Add the second initiator solution and preemulsion II dropwise to the reaction solution containing core A to carry out the second stage polymerization reaction, obtaining a reaction solution containing block polymer A and intermediate layer B. Add an accelerator solution to the reaction solution containing block polymer A and intermediate layer B, and then add the third initiator solution and preemulsion III dropwise to carry out the third stage polymerization reaction, obtaining a reaction solution containing acrylic resin. Step S3: The reaction solution containing acrylic resin is mixed with the second oxidant solution and the second reducing agent solution for reaction, and then a neutralizing agent solution and a coagulant solution are mixed in. After solid-liquid separation, the mixture is dried to obtain acrylic resin. Preferably, when the preemulsion II contains a portion of the second hard monomer, in step S2, after adding 50-70% of the preemulsion II to the reaction solution containing the core A, the remaining portion of the second hard monomer is added to the preemulsion II while simultaneously adding the preemulsion II to the reaction solution containing the core A; more preferably, the mass of the second hard monomer added to the preemulsion II accounts for 25%-65% of the total mass of hard monomers in the raw materials for preparing the intermediate layer B.

9. The use of an acrylic resin according to any one of claims 1-4 or an acrylic resin prepared by any one of claims 5-8 in improving the optical and / or mechanical properties of a thermoplastic resin; optionally, the thermoplastic resin includes polymethyl methacrylate.

10. A modified PMMA resin, characterized in that, Includes the acrylic resin according to any one of claims 1-4 or the acrylic resin prepared by any one of claims 5-8, and polymethyl methacrylate; Optionally, the acrylic resin and the polymethyl methacrylate are in a ratio of 0.5~2:1~5.

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